Well pumping apparatus



Nov. 6, 1962 H. E. WARD 3,062,154

WELL PUMPING APPARATUS Filed July 27, 1959 o o I /36 |6- 0 IA Q FIG. 2

HIS AGENT United States Patent 3,062,154 WELL PUMPING APPARATUS HaroldE. Ward, Bakersfield, Califi, assignor to Shell Oil Company, acorporation of Delaware Filed July 27, 1959, Ser. No. 829,801 4 Claims.(Cl. 103206) This invention relates to well pumping apparatus andpertains more particularly to an oil well pumping unit for use inpumping oil wells wherein there is substantial fluid hammer and shockloading on the downhole equipment.

More than three-quarters of all the oil wells in the United States areproduced by artificial means, the commonest of which is a reciprocatingoil well pump positioned near the bottom of the well or adjacent theproducing formation. In many of these wells the downhole equipment,principally the string of production tubing, the sucker rods and thereciprocating pump, is subjected to forces which cause deterioration orbreak-down at a rate faster than normal. Fluid hammer and shock loading,caused partially by closure of the valves in the pumping apparatus, arefactors which contribute to the deterioration of the equipment.

It is therefore a primary object of the present invention to provide awell pumping appartus adapted to be positioned in a well above areciprocating pump to reduce the fluid hammer and shock loading on thedownhole equipment.

As a result of the shocks that occur during the pumping cycle of areciprocating oil well pump, a number of leaks may occur in theproduction tubing string either at the threaded joints or due tolongitudinal splits in the wall thereof. Additionally, the downhole pumpis subjected to greater wear due to expansion and contraction of thepump barrel as the result of these shock loads.

It is therefore another object of the present invention to provide awell pumping apparatus adapted to decrease the shock loading on thedownhole equipment so as to reduce the frequency of leaks in the tubingstring and to lengthen the life of the pump.

These and other objects of this invention will be understood from thefollowing description taken with reference to the drawing, wherein:

FIGURE 1 is a diagrammatic view, taken partially in longitudinalcross-section, illustrating the apparatus of the present invention whenconnected to a reciprocating-type pump in a well wherein the pump isbeing reciprocated by a prime mover located at the surface; and

FIGURE 2 is a diagrammatic view taken in longitudinal cross-section ofthe pulsation dampening apparatus of the present invention.

Referring to FIGURE 1 of the drawing, a prime mover of a pumping unit isshown positioned adjacent a wellhead 11 on the surface of the earth 12.Extending downwardly from the wellhead 11 is a tubing string 13. Areciprocating-type pumping unit comprising a pump plunger 14, standingvalve 15, and traveling valve 16 is fixedly secured in the bottom of thetubing string 13 with a plunger 14 and traveling valve 16 mounted forvertical reciprocating motion therein. it is assumed that the outersurface of the pump plunger 14 is provided with one or more fluidsealing members or swab cups 17 of a type well known to the art forsealing the space between the outer wall of the pump plunger and theinner wall of the oil tubing string.

Fixedly, secured to the top of the pump above the traveling valve 16, asby a threaded rod 18 is a pulsation dampener 21 which is described ingreater detail with regard to FIGURE 2. The pulsation dampener 21comprises an elongated tubular housing in which a piston ice element 22is mounted for sliding axial movement therein. Preferably, the pistonelement 22 may comprise a pair of swab cups or rubbers, as illustrated,mounted in back to back fashion and fixedly secured together with theconcave portions facing in opposite directions.

At one end of the pulsation dampener 21, one or more ports are providedin communication between the interior of a tubular housing 21 and thespace outside. These ports 23 may either pass through the wall of thepulsation dampener or through the closure member 24 which closes thelower end of the dampener. The upper end of the pulsation dampener 21may be closed in a similar manner by another closure means 25 which isfixedly secured to the top of the dampener in any fiuidtight manher, asby screw threads or welding. Preferably, the top closure means 25 isprovided with a charging conduit 26 which is normally closed by a valve27 which is preferably recessed, as at 28, below the outer surface ofthe pulsation dampener so that the valve does not rub against the innerwall of the tubing string when the pulsation dampener 21 is reciprocatedin said string.

A threaded pin 3d or other suitable connecting means is provided at thetop of the pulsation dampener for connecting it to the lower end of asucker rod string 31, as shown in FIGURE 1. In the event that the fluidports 23 are provided through the side walls of the pulsation dampener21, suitable stop means are provided in the interior of the pulsationdampener 21 to prevent the piston element 22 from descending far enoughto uncover the ports 23. Thus, while stop means 32 may be fixedlysecured to the inner Wall of the pulsation dampener and extend inwardlytherefrom, a stop means preferably takes the form of a rod 33 attachedto the bottom side of the piston member 22. The length of the rod 33 issuch that its lower end will contact the closure means 24 of thepulsation dampener 21 before the uppermost ports 23 are in communicationbetween the space outside the pulsation dampener and the space withinthe dampener above the piston means 22. In the event that the ports 23only extend through the bottom closure member 24 of the pulsationdampener, the stop means 32 or 33 may be eliminated. The stop means 32or 33 may include a shock absorb-er spring 36 to decrease mechanicaldamage due to pounding the bottom end of the pulsation dampener.

In order to form a more effective seal at all times, a small amount ofliquid such as water or oil 34 is placed above the piston element 22 inorder to retain the gas under pressure thereabove. Prior to use, thepulsation dampener of the present invention is charged, through chargingvalve 27 and conduit 26, with a gas such as nitrogen to a predeterminedpressure of about 0.4 pound per square inch per foot of depth to whichthe pump will be run. The charging pressure depends upon the wellconditions under which the present apparatus is to be used.

During operation of the pumping well utilizing the present invention,the pulsation dampener 21, after being charged above the piston element22 with a gas, is connected by means of threaded pin 30 to the lower endof sucker rod string 31, as illustrated in FIGURE 1. The threaded pin 18on the other end of the pulsation dampener 21 is connected to the top ofthe pump plunger, after which both elements are lowered by means of thesucker rod string to the bottom or at any predetermined level within theoil tubing string 31. After securing the pump therein in anyconventional manner, the sucker rod string 31 is connected to its primemover 10 and pumping operations are carried out.

During pumping operations, when the well fluid being lifted by the pumpplunger 14 fills the tubing string 13 to the top thereof well fluidenters ports 23 and substantially fills the space within the pulsationdampener 21 below its piston element 22. As shocks are imposed on thewell fluid during each pumping cycle, the scaling piston member 22 movesup and down inside the tubular body of the dampener 21 to allow the gasin the upper part of the dampener 2 1 to expand or to compress it. Theexpansion and contraction of the gas in the pressure chamber above thepiston element 22 dampens the shocks generated in the fluid andminimizes their detrimental effects on the pumping equipment, primarilythe pump and the tubing string. Normally, the pulsation dampener ischarged with a gas to the anticipated average operating pressure withinthe well.

In one test, fluid pound or shocks due to the pumping equipment werefound to be severe under a variety of operating conditions including onein which there was 1500 barrels per day gross production, 95% water cut,production being carried out .at a 1530 foot fluid producing level witha 3-inch by 2%-inch pump positioned at 1655 feet and the pumping unitoperating with an 80-inch stroke at about 20 strokes per minute. Priorto installing the apparatus of the present invention 11 tubing splitsand collar thread leaks occurred in the tubing string within afour-month period. In the seven months after installing the apparatus ofthe present invention, only one tubing split had occurred. In addition,the loads on the pumping unit had been reduced substantially, with thepeak polished rod load being reduced fro-m 9200 pounds to 8000, whilethe peak torque had been reduced from 178,000 inch pounds to 144,000.

I claim as my invention:

1. A well pumping installation comprising an elongated fluid-filledstring of pipe extending from the earths surface down into a well, areciprocating-type well pump fixedly positioned within said pipe stringat a point below the normal liquid level in the well, an elongatedtubular pulsation dampener of a diameter less than the inner diameter ofthe pipe string, the lower end of said dampener being fixedly secured tothe movable portion of said pump for reciprocation therewith, fluid portmeans open at all times through the wall of said pulsation dampener incommunication between the space inside thereof and the fluid in the pipestring surrounding said pulsation dampener, movable piston means mountedin said pulsation dampener dividing the pulsation dampener in twochambers one of said chambers being fluidtight and adapted to be chargedwith a compressible fluid, a sucker rod string affixed at its lower endto the pulsation dampener and extending upwardly through said pipestring to the surface, and prime mover means positioned at the surfaceand operatively connected to the upper end of said sucker rod string forvertically reciprocating said sucker rod string.

2. A well pumping installation comprising an elongated fluid-filledstring of pipe extending from the earths surface down into a well, areciprocating-type well pump having standing and traveling valves and aplunger, said well pump being fixedly positioned within said pipe stringat a point below the normal liquid level in the well, an elongatedtubular pulsation dampener of a diameter less than the inner diameter ofthe pipe string, the lower end of said dampener being fixedly secured tothe movable portion of said pump for reciprocation therewith, fluid portmeans open at all times through the wall of said pulsation dampener incommunication between the space inside thereof and the fluid in the pipestring surrounding said pulsation dampener, movable piston means mountedin said pulsation dampener dividing the pulsation dampener in twochambers one of said chambers being fluid:

tight and adapted to be charged with a compressible fluid, a sucker rodstring aflixed at its lower end to the pulsation dampener and extendingupwardly through said pipe string to the surface, prime mover meanspositioned at the surface and operatively connected to the upper end ofsaid sucker rod string for vertically reciprocating said sucker rodstring.

3. A well pumping installation comprising an elongated fluid-filledstring of pipe extending from the earths surface down into a well, areciprocating-type well pump having standing and traveling valves and aplunger, said well pump being fixedly positioned within said pipe stringat a point below the normal liquid level of the well, an elongatedtubular pulsation dampener of a diameter less than the inner diameter ofthe pipe string, the lower end of said dampener being fixedly secured tothe movable portion of said pump for reciprocation therewith, a suckerrod string afiixed at its lower end to the pulsation dampener andextending upwardly through said pipe string to the surface, prime movermeans positioned at the surf-ace and operatively connected to the upperend of said sucker rod string for vertically reciprocating said suckerrod string, said pulsation dampener comprising an elongated tubular bodymember closed at both ends, a slidable piston element movably positionedin said body member and dividing said body member into two chamber, oneof said chambers being charged with gas, and fluid port means throughthe wall of said body member in communication between the space outsidethereof and the chamber? A on the other side of the piston element.

4. A well pumping installation comprising an elongated fluid-filledstring of pipe extending from the earths surface do-wn into a well, areciprocating-type well pump having standing and traveling valves and aplunger, said well pump being fixedly positioned within said pipe stringat a point below the normal liquid level in the well, an elongatedtubular pulsation dampener of a diameter less than the inner diameter ofthe pipe string, the lower end of said dampener being fixedly secured tothe movable portion of said pump for reciprocation therewith, a suckerrod string aflixed at its lower end to the pulsation dampener andextending upwardly through said pipe string to the surface, prime movermeans positioned .at the surface and operatively connected to the upperend of said sucker rod string for vertically reciprocating said suckerrod string, said pulsation dampener comprising an elongated tubular bodymember closed at both ends, a slidable piston element movably positionedin said body member and dividing said body member into two chambers, oneof said chambers being charged with gas, fluid port means through thewall of said body member in communication between the space outsidethereof and the chamber on the other side of the piston element, stopmeans carried within said body member for limiting the travel of saidpiston element to prevent escape of gas through said port means, and aliquid seal carried on said piston element within said gas-chargedchamber.

References Cited in the file of this patent UNITED STATES PATENTS858,901 Nagel July 2, 1907 2,172,602 Williams Sept. 12, 1939 2,633,368Ross Mar. 31, 1953 2,814,462 De Jarnet Nov. 26, 1957 2,815,928 BodineDec. 10, 1957 2,838,283 Simmonds June 10, 1958 2,936,860 Peras May 17,1960

